Apparatus for defining a passageway through a composition

ABSTRACT

An apparatus for defining a passageway through a composition between first and second locations. The apparatus has a cable pulling assembly and a support for the cable pulling assembly. The cable pulling assembly has a capstan assembly, with a part of the capstan assembly guided in movement around a first axis and engageable with a cable connected to a mole so as to cause a cable engaged by the part of the capstan assembly to be pulled as the part of the capstan assembly is driven around the first axis. The part of the capstan assembly has a circumferential groove, bounded by a surface and extending around the first axis, for reception of a cable to be pulled. The groove is configured so that a circumferentially localized force is applied by the groove surface to a cable operatively positioned in the groove tending to avoid circumferential slippage between the part of the capstan assembly and the cable operatively positioned in the groove.

CROSS REFERENCE

This application is a continuation-in-part of co-pending applicationSer. No. 10/781,236 filed Feb. 8, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to cable pulling systems and, more particularly,to a system for drawing a mole through a composition to create apassageway between first and second spaced locations.

2. Background Art

It is well known in the industry to draw a mole through a composition todefine a passageway through the composition between first and secondspaced locations. It is known to use this method to replace collapsedconduits, such as those used for sewage, or for other applications. Tocarry out this process, access space is required at each of the firstand second locations. A cable is directed from the second locationthrough the existing conduit back to the first location at which thecable end is connected to an appropriately configured mole. The mole isengaged with a length of a replacement conduit in such a manner that theconduit will follow translatory movement of the mole. At the secondlocation, a cable pulling mechanism is employed. The cable pullingmechanism, which is commonly hydraulically actuated, is braced againstthe composition and operated to draw the mole through the compositionfrom the first location to the second location. The operator, who issituated at the second location, must monitor the advancement of themole and disable the cable pulling mechanism at the appropriate time toprevent the mole from detrimentally contacting any part of the cablepulling mechanism and/or its support structure.

One known cable pulling mechanism is disclosed in U.S. Pat. No.6,305,880. In that mechanism, the mole is advanced, through repeatedpulling strokes, over its entire travel path between the first andsecond locations. In a typical pulling cycle, the mole will be advancedon the order of four inches. Each successive cycle must be initiated byan operator. While this system has been commercially successful, it hasa number of inherent drawbacks.

First of all, as a result of the stepwise application of the pullingforce, the mole, and following conduit, come to rest each time themechanism is at the dwell stage for a pulling cycle. As this occurs, thestationary mole and conduit may become temporarily lodged before thepulling force can be reapplied thereto. To reinitiate movement of themole, a greater force may be required than would be if the mole movementwere not interrupted. This places greater demands on the cable pullingstructure, the cable, the mole, the conduit, and the structureoperatively connecting the mole to the cable and conduit. As a result,there is the potential for premature failure of one or more of thesecomponents and a potential reduction in the anticipated life of theoverall system.

To address this problem, the system components may be made withincreased capacity to ensure reliable operation and an adequately longlife for the equipment. This may significantly increase the overallsystem costs which may have to be passed on to the system purchaser.

Another problem with the above prior art system is that the cablepulling mechanism is required to have potentially a large number ofcomponents to coordinatingly interact to alternatingly apply and releasethe pulling force on the cable. Generally, the more complicated systemsbecome, the more prone they are to malfunction. Further, complicatedsystems are inherently more expensive than their simpler counterparts.

Still further, the above system has the drawback that the process formoving the mole between the first and second locations may be timeconsuming by reason of the stepwise advancement of the mole. These typesof systems are generally designed to advance a mole through relativelydense compositions that offer a high resistance to movement of the mole.In some environments, such as in loose soil or a preexisting passageway,a significantly lesser resistance to mole movement may be encountered.However, the system operator is nonetheless required to operate thesystem in the same manner, initiating each advancing cycle, so that themole moves at a relatively slow rate from the first location to thesecond location. Since these systems may require two or more individualsto set them up and monitor their operation, the number of man hoursrequired to complete a job may be significant.

To the knowledge of the inventors herein, the industry has not utilizeda cable pulling mechanism that is operable to continuously exert apulling force on a mole to form or enlarge a passageway through acomposition, as described above. Even had the industry looked in thisdirection, as a practical matter there has been lacking a compact unitwith the required cable pulling capabilities that could be transportedto different sites.

At some sites, the unit is required to be set up for operationunderground or otherwise in a restricted space. In these tight quarters,a continuous cable pulling mechanism represents a particular challengeto designers. With a conventional capstan configuration, a V-shapedgroove is formed continuously around an annular element that is drivenaround an axis. The surface bounding the groove and cable are relativelyconfigured and dimensioned so that the cable wedges into the groovesurface. This wedging action produces a traction force that causes thecable to follow movement of the annular capstan element around the axis.

Typically, capstans are made with a groove with a uniformcross-sectional configuration around the entire circumferential extentthereof. A cable to be pulled is wrapped around the capstan within thegroove so that the center line of the wrapped cable resides in a singleplane that is orthogonal to the rotary axis for the annular capstanelement. The magnitude of the traction force is dictated by the degreeof wrapping of the cable around the capstan. The cable is typicallywrapped through significantly less than 3600 around the capstan so thatthere is no interference between the cable at locations at which itinitially contacts the capstan and departs therefrom.

The traction force may be increased by increasing the diameter of thecapstan so as to increase the contact area between the annular capstanelement and the wrapped cable. However, given typical space constraints,there are limitations placed on the dimensions of the capstan.

An alternative way to increase the contact area between the cable andcapstan is to cause wrapping through in excess of 3600 around thecapstan. This requires the formation of a spiral groove pattern on theannular capstan element. As a result, the axial dimension of the capstanincreases, as does potentially the cost of the capstan manufacture.Additionally, the use of multiple turns of cable on a capstan causescomplications for the system operator. The operator must manipulate thecable around the capstan in a manner that may be inconvenient orimpractical in quarters that are close. Further, the inherent stiffnessof a cable may make it difficult to produce the multiple wraps and tomaintain the cable in the groove in a proper manner preparatory tostartup.

Designers of this type of system strive to devise portable systems thatcan be economically manufactured, will reliably perform in potentiallysevere environments, can be conveniently and efficiently set up,operated, and broken down, and will perform reliably for an adequate-lifetime. In the interest of economy, it is also a goal for designersof these systems to avoid the unnecessary expenditure of man hours fortheir operation.

SUMMARY OF THE INVENTION

In one form, the invention is directed to an apparatus for defining apassageway through a composition between first and second locations. Theapparatus has a cable pulling assembly and a support for the cablepulling assembly. The cable pulling assembly has a capstan assembly,with a part of the capstan assembly guided in movement around a firstaxis and engageable with a cable connected to a mole so as to cause acable engaged by the part of the capstan assembly to be pulled as thepart of the capstan assembly is driven around the first axis. The partof the capstan assembly has a circumferential groove, bounded by asurface and extending around the first axis, for reception of a cable tobe pulled. The groove is configured so that a circumferentiallylocalized force is applied by the groove surface to a cable operativelypositioned in the groove tending to avoid circumferential slippagebetween the part of the capstan assembly and the cable operativelypositioned in the groove.

The apparatus may be provided in combination with a cable and a moleattached to the cable.

In one form, the groove extends continuously around the first axis.

In one form, the groove has an axial center and the axial center of thegroove at a first circumferential location is spaced axially from theaxial center of the groove at a second circumferential location.

In one form, the groove has a circumferential extent and the axialcenter of the groove has a curved shape over at least a portion of thecircumferential extent of the groove.

The axial center of the groove may have a wave shape over at least aportion of the circumferential extent of the groove.

In one form, the groove surface defines an axial projection which causesthe circumferentially localized force to be applied to a cable undertension within the groove.

In one form, the groove surface has axially spaced side portions whichconverge to a radially opening bottom portion and the axial projectionis defined by one of the axially spaced side portions.

The groove may extend in a spiral pattern around the first axis.

In one form, the cable pulling assembly has a drive and a gear assemblyoperatively engaged between the drive and the part of the capstanassembly to cause the part of the capstan assembly to be driven aroundthe first axis.

The gear assembly may be a planetary gear assembly.

The invention is further directed to an apparatus for defining apassageway through a composition between first and second locations,which apparatus has a cable pulling assembly and a support for the cablepulling assembly. The cable pulling assembly has a capstan assembly,with a part of the capstan assembly guided in movement around a firstaxis and engageable with a cable connected to a mole so as to cause acable engaged by the part of the capstan assembly to be pulled as thepart of the capstan assembly is driven around the first axis. The partof the capstan assembly has a circumferential groove, bounded by asurface and extending around the first axis, for reception of a cable tobe pulled. The groove extends continuously around the first axis and hasan axial center. The axial center of the groove at a firstcircumferential location is spaced axially along the part of the capstanassembly from the axial center of the groove at a second circumferentiallocation.

The apparatus may be provided in combination with a cable and a moleattached to the cable.

In one form, the groove has a circumferential extent and the axialcenter of the groove has a curved shape over at least a portion of thecircumferential extent of the groove.

In one form, the axial center of the groove has a wave shape over atleast a portion of the circumferential extent of the groove.

In one form, the groove surface defines an axial projection which causesa circumferentially localized force to be applied to a cable undertension within the groove.

The groove surface has axially spaced side portions which converge to aradially opening bottom portion. In one form, the axial projection isdefined by one of the axially spaced side portions.

In one form, the cable pulling assembly includes a drive and a gearassembly operatively engaged between the drive and the part of thecapstan assembly to cause the part of the capstan assembly to be drivenaround the first axis.

The gear assembly may be a planetary gear assembly.

The invention is further directed to a cable pulling assembly having acapstan assembly having a part with a groove for receiving a cable to bepulled and a drive through which the part of the capstan assembly isdriven around a first axis to cause a cable operatively positioned inthe groove to be pulled. The groove has a circumferential extent aroundthe first axis. The groove is configured so that a circumferentiallylocalized force is applied by the groove surface to a cable operativelypositioned in the groove, tending to avoid circumferential slippagebetween the part of the capstan assembly and a cable operativelypositioned in the groove.

The cable pulling assembly may be provided in combination with a cableand mole which is connectable to the cable to follow movement of thecable through a composition to form a passageway in the composition.

The groove may extend continuously around the first axis.

In one form, the groove has an axial center, and the axial center of thegroove at a first circumferential location is spaced axially along thepart of the capstan assembly from the axial center of the groove at asecond circumferential location.

In one form, the center of the groove has a curved shape over at least aportion of the circumferential extent of the groove.

The center of the groove may have a wave shape over at least a portionof the circumferential extent of the groove.

In one form, the groove is bounded by a surface and the surface definesan axial projection which causes the circumferentially localized forceto be applied to a cable under tension within the groove.

In one form, the surface of the groove has axially spaced side portionswhich converge to a radially opening bottom portion and the axialprojection is defined by one of the axially spaced side portions.

A gear assembly may be operatively engaged between the drive and capstanassembly part to cause the part of the capstan assembly to be drivenaround the first axis.

The gear assembly may be a planetary gear assembly.

The invention is further directed to a cable pulling assembly having acapstan assembly with a part with a groove for receiving a cable to bepulled and a drive through which the part of the capstan assembly isdriven around the first axis to cause a cable operatively positioned inthe groove to be pulled. The groove has a circumferential extent aroundthe first axis. The axial center of the groove at a firstcircumferential location is spaced axially along the part of the capstanassembly from the axial center of the groove at a second circumferentiallocation.

The apparatus may be provided in combination with a cable and mole thatis connectable to the cable to follow movement of the cable through acomposition to form a passageway in the composition.

The groove has a circumferential extent. In one form, the axial centerof the groove has a curved shape over at least a portion of thecircumferential extent of the groove.

The axial center of the groove may have a wave shape over at least aportion of the circumferential extent of the groove.

In one form, the groove is bounded by a surface and the surface definesan axial projection which causes a circumferentially localized force tobe applied to a cable under tension within the groove.

In one form, the surface of the groove has axially spaced side portionswhich converge to a radially opening bottom portion and the axialprojection is defined by one of the axially spaced side portions.

The cable pulling assembly may further include a gear assemblyoperatively engaged between the drive and the part of the capstanassembly to cause the part of the capstan assembly to be driven aroundthe first axis. The gear assembly may be a planetary gear assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an exemplary environment forpracticing the present invention and showing, in schematic form, anapparatus, according to the present invention, for defining a passagewaythrough a composition between first and second spaced locations;

FIG. 2 is a flow diagram showing the steps of advancing a mole to definea passageway through a composition between first and second locations,according to the present invention;

FIG. 3 is a perspective view of the inventive apparatus in FIG. 1 andincluding a cable pulling assembly and a support therefor, with thesupport including a frame, to which the cable pulling assembly isreleasably attached, a reaction plate, and a reaction cage between theframe and reaction plate;

FIG. 4 is a side elevation view of the apparatus in FIG. 3;

FIG. 5 is a rear elevation view of the apparatus in FIGS. 3 and 4;

FIG. 6 is a perspective view of the reaction plate on the apparatus ofFIG. 3-5;

FIG. 7 is a perspective view of the reaction cage on the apparatus inFIGS. 3-5;

FIG. 8 is a plan view of the reaction cage in FIG. 7;

FIG. 9 is a plan view of the frame on the apparatus of FIGS. 3-5;

FIG. 10 is a side elevation view of the frame in FIG. 9;

FIG. 11 is a perspective view of the frame in FIGS. 9 and 10;

FIG. 12 is a rear elevation view of the frame in FIGS. 9-11;

FIG. 13 is an enlarged, side elevation view of a traction supportassembly that is part of the cable pulling assembly in FIGS. 3-5;

FIG. 14 is a rear elevation view of the traction support assembly inFIG. 13;

FIG. 15 is an elevation view of the traction support assembly in FIGS.13 and 14, from the side opposite that in FIG. 13;

FIG. 16 is a fragmentary, schematic representation showing therelationship between the cable pulling assembly and frame on theapparatus in FIGS. 3-5 and with the cable pulling assembly shown in apreassembly position in solid lines and in an operative position indotted lines;

FIG. 17 is an enlarged, perspective view of an operating componentpackage assembly that is part of the cable pulling assembly and attachedto the traction support assembly in FIGS. 13-15;

FIG. 18 is an enlarged, side elevation view of the operating componentpackage assembly in FIG. 17;

FIG. 19 is an enlarged, rear elevation view of the operating componentpackage assembly in FIGS. 17 and 18;

FIG. 20 is an exploded, perspective view of the operating componentpackage assembly in FIGS. 17-19;

FIG. 21 is an enlarged, cross-sectional view of the operating componentpackage assembly taken along line 21-21 of FIG. 19;

FIG. 22 is an enlarged, cross-sectional view of the operating componentpackage assembly taken along line 22-22 of FIG. 19;

FIG. 23 is a cross-sectional view of the operating component packageassembly taken along line 23-23 of FIG. 18;

FIG. 24 is an enlarged, perspective view of a capstan assembly that ispart of the operating component package assembly of FIGS. 17-23, andincluding a cable-engaging part with a groove in which a cable isengaged to be advanced by the cable pulling assembly;

FIG. 25 is a rear elevation view of the capstan assembly in FIG. 24;

FIG. 26 is an enlarged, perspective view of a planet gear on a planetarygear assembly on the operating component package assembly, for drivingthe cable-engaging part of the capstan assembly around an axis;

FIG. 27 is an enlarged, perspective view of a sun gear on the planetarygear assembly;

FIG. 28 is an enlarged, fragmentary, schematic representation of thecable-engaging part on the capstan assembly in FIGS. 24 and 25 andshowing the cooperation between a cable and the groove on thecable-engaging part;

FIG. 29 is a view as in FIG. 28 with either a smaller cable or the cablein FIG. 28 drawn to have an effectively reduced diameter;

FIG. 30 is an enlarged, perspective view of a drive/hydraulic motorassembly for operating the cable pulling assembly on the apparatus inFIGS. 3-5;

FIG. 31 is a schematic, rear elevation view, corresponding to that inFIG. 25, and showing a portion of the groove on the capstan assemblywith a cable operatively positioned in the groove; and

FIGS. 32-37 are views corresponding to that in FIG. 31 and showingalternative groove configurations, according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIG. 1, a representative environment is shown at 10 for the practiceof the present invention. An apparatus, according to the invention, isshown at 12 for defining a passageway through a composition at 14between a first location 16 and a second location 18. The composition 14may be any naturally occurring composition, a composition that isformed, as through construction, or the like, or a combination thereof.In this particular application, a collapsed conduit 20, extendingbetween the first and second locations 16,18, is being replaced. Theprocess for operating the inventive apparatus 12 will now be describedwith reference additionally to the flow diagram shown in FIG. 2.

Initially, a cable 22 is directed between the first and second locations16,18, as shown at block 24. To accomplish this, the cable 22 can bedirected from either the first location 16 to the second location 18, oralternatively, from the second location 18 to the first location 16. Ifthe condition of the conduit 20 permits, the cable 22 may be directedtherethrough without resistance. Alternatively, conventional means,known to those skilled in the art, may be utilized to direct the cable22 between the first and second locations 16,18. The invention alsocontemplates that the cable 22 could be directed between the first andsecond locations 16,18 without any preformed passageway, as defined bythe conduit 20, as by preforming a small passageway therefor, or byforcibly advancing the cable 22 through the composition between thefirst and second locations 16, 18. Again, those skilled in the art arefamiliar with conventional means that can be utilized to direct thecable 22 through the composition 14 between the first and secondlocations 16,18, without any preexisting passageway.

At the first location 16, a mole 26 is attached to the cable 22, asshown at block 28. In the event that the cable 22 is directed from thefirst location 16 towards the second location 18, the mole 26 can bepre-attached to the cable 22. Those skilled in the art are well versedin the selection of a mole to penetrate the specific composition 14 andgenerate an opening of the desired dimensions therethrough.

A conduit 30 is attached to the mole 26, as shown at block 32. An end ofthe conduit 30 is attached to the mole 26 to follow movement thereof asthe cable 22 draws the mole 26 from the first location 16 to the secondlocation 18. Suitable connecting structures are also well known to thoseskilled in this art.

The cable 22 is then engaged with a cable pulling assembly 34, as shownat block 36. The cable pulling assembly 34 is carried on a support 38.The cable pulling assembly 34 may be permanently mounted to the support38, but is more preferably separably mounted thereto, as explained ingreater detail below. The support 38 bears against the composition 14 totransfer to the composition 14 a reaction force that is generated as thecable pulling assembly 34 draws the cable 22 between the first location16 and the second location 18. It should be understood that while thesupport 38 is described throughout as bearing against the composition14, it is also contemplated that the support 38 could bear against anyother firm structure that may be integrated into the composition 14, orseparate therefrom. The description of the support 38 as bearing against“the composition 14” hereinbelow is intended to encompass bearingagainst any firm structure.

The apparatus 12 is placed in an operative position at the firstlocation 18, as shown at block 40. The apparatus 12 can be pre-assembledand directed downwardly in that state through an opening 42 to adjacentthe second location 18, or directed through the opening 42 in parts andassembled at the second location 18, as hereinafter described.

As shown at block 44, the cable pulling assembly 34 is operated by auser/operator 46 through a control 48 to exert a pulling force on thecable 22, as indicated by the arrow 50. The pulled cable 22 is thendirected away from the cable pulling assembly 34, as indicated by thearrow 52, and may be accumulated at the second location 18, or directedoutwardly through the opening 42.

The cable pulling assembly 34 may be continuously operated to cause apulling force on the cable 22 to be continuously applied through thecable pulling assembly 34 to the cable 22 and therethrough to the mole26 to thereby cause the mole 26 to be advanced in a travel path equal tothe entire distance D between the first and second locations 16,18, orat least a substantial distance D1 that is less than the distance D. Thedistance D may be, for example, several feet up to potentially a hundredor more feet. It is contemplated that the mole 26 be moved under acontinuously applied force through at least the substantially shorterdistance D1, that is less than the distance D, but on the order of onefoot or more.

Once the conduit 30 is drawn in a manner that a sufficient lengththereof is exposed at the first and second locations 16,18, theapparatus 12, mole 26, and cable 22 are separated from the conduit 30,as shown at block 54. The apparatus 12, mole 26, and cable 22 can thenbe removed from the site, as shown at block 56. The apparatus 12 can beremoved as a unit or broken down to facilitate removal andtransportation in parts.

In the depicted environment 10, the first and second locations 16,18 areshown underground. In this case, the conduit 30 can be drawn from asupply 58 thereof, above ground, to be advanced in followingrelationship with the mole 26, between the first and second locations16,18. In this environment 10, the operator/user 46 is likewise locatedunderground. A vertical opening 60 can be formed to a sufficientdiameter to allow the conduit 30 to be drawn from the supply 58 to bepresented at the first location 16, and drawn through the composition 14from the first location 16 to the second location 18, without damagethereto.

It should be understood that the invention is not limited to anunderground application and can be used in any environment in which amole, or other like leading structure, is to be drawn by a cable througha composition, with or without a partial or full passage opening.Further, it is not required that a conduit be drawn through thecomposition, as solid cable or other material could be connected tofollow the movement of the mole, or the like, in the same manner, toextend the same between corresponding first and second locations.

Further, in the event that a conduit is advanced between the first andsecond locations, the nature of the conduit is not in any way limited.The conduit could be used to define a receptacle for cables, such as inthe telecommunications industry, to communicate water, that may be freshwater or sewage, etc.

Referring now to FIGS. 3-5, one specific form of the inventive apparatus12 is shown. The apparatus 12 consists of the cable pulling assembly 34,which is mounted in an operative position on the support 38. The support38 consists of a frame 64 to which the cable pulling assembly 34 isreleasably, operatively connected, a reaction plate 66, and a reactioncage 68 acting between the frame 64 and reaction plate 66. With theframe 64, reaction cage 88, reaction plate 66, and reaction cage 68assembled, a downwardly facing support surface at 70 is defined bycoplanar surfaces on the frame 64, reaction cage 88, and reaction plate66. The frame 64 has a flat surface 72, with the reaction plate 66having flat surfaces 74,76 defined on horizontally projecting feet 78,80, respectively, and flat surfaces 82 (one shown in FIG. 4) onhorizontally projecting feet 83 (one shown in FIG. 4). A reference planeP, coincident with the surfaces 72, 74, 76, 82, is orthogonal to a planeP1 that coincides with an enlarged, substantially flat surface 84 on thereaction plate 66. With this configuration, the surfaces 72, 74, 76, 82can be placed against an upwardly facing surface 86, as shown in FIG. 1.With the apparatus 12 supported in this manner, the reaction platesurface 84 can be braced against a vertically extending surface 88 onthe composition 14 at the second location 18.

The reaction plate 66 has an opening 90 through which the cable 22 canbe drawn by the cable pulling assembly 34. As the cable 22 is drawn bythe cable pulling assembly 34 in the direction of the arrow 92 in FIG.4, a reaction force is generated which is transferred from the cablepulling assembly 34 through the frame 64, reaction cage 58 and reactionplate 66 to the composition 14 which, as previously discussed, may be anexisting component or any other preexisting or added structure that isstable and sufficiently rigid to withstand the reaction force generatedduring operation of the cable pulling assembly 34.

As depicted in FIG. 4, the cable 22 is drawn generally in the pathindicated by the dotted line at 94. The cable 22 moves through theopening 90 in the reaction plate 66, through the reaction cage 68, and avertically extending wall 96 on the frame 64, to engage an annularcable- engaging part 98 (FIG. 5) at approximately the 12 o'clockposition thereon. The cable 22 wraps in a clockwise direction in FIG. 4around the cable-engaging part 98 and departs from the cable-engagingpart 98 at approximately the 9 o'clock position thereon to be directedupwardly for appropriate accumulation as the cable pulling assembly 34is operated. As explained in greater detail below, the cable-engagingpart 98 is driven about an axis 102 to cause continuous advancement ofthe cable 22 in the aforementioned path, shown by the dotted line 94 inFIG. 4.

A drive/hydraulic motor assembly at 104, in communication with apressurized hydraulic fluid supply 106, is operable to drive thecable-engaging part 98 around the axis 102, as is also described ingreater detail below. According to the invention, the drive/hydraulicmotor assembly 104 can be continuously operated to cause thecable-engaging part 98 to continuously exert a pulling force on thecable 22 and therethrough to the mole 26 to cause the mole 26 to beadvanced. The mole 26 is thus capable of being advanced a substantialdistance under this constant pulling force. A “substantial distance”, asused herein, is intended to be on the order of a foot or more. Morepreferably, the entire distance to be traversed by the mole 26 throughthe composition 14 is travelled under a continuous force applicationthrough the cable 22 to the mole 26. This obviates the incorporation ofa conventional-type mechanism typically operated by applying andreleasing a pulling force on the cable 22. An actuator 108, associatedwith the control 48, is manually operable by the user/operator tocontrol the drive/hydraulic motor assembly 104. Thus, the user/operatorhas the ability to cause the pulling force to be applied on the cable 22through the cable pulling assembly 34 continuously, or at desiredintervals, to cause the mole 26 to be advanced a substantial distanceunder a constant pulling force. The drive/hydraulic motor assembly 104can be continuously operated as the mole 26 moves fully from the firstlocation 16 to the second location 18.

A switch assembly 1 10 is provided to disable the drive/hydraulic motorassembly 104 and thereby stop operation of the cable pulling assembly 34with the mole 26 advanced to a predetermined position relative to thecable pulling assembly 34. Accordingly, the advancement of the cable 22and the mole 26 will be automatically stopped so that no operatorintervention is required to avoid drawing of the mole 26 against anypart of the support 38 or cable pulling assembly 34 as might inflictdamage thereon.

The apparatus 12 preferably has a modular construction which allows itto be transported in separate pieces and assembled on site. In thisembodiment, the cable pulling assembly 34, frame 64, reaction cage 68,and reaction plate 66 are formed as separable components.

Referring now additionally to FIGS. 6-8, the reaction plate 66 has areinforced wall 112 through which the cable opening 90 is formed. Theflat surface 84 is defined on one side of the wall 112. Mounting tabs114,116,118,120 project from the side of the wall 112 opposite that onwhich the surface 84 is defined. With the reaction plate 66 and reactioncage 68 in the assembled relationship shown in FIGS. 3-5, mounting tabs122,124,126,128 on the reaction cage 68 situate adjacent to the mountingtabs 114,116,118,120, respectively, to allow releasable locking pins 130to be directed through bores in each of the adjacent, paired mountingtabs 114,122; 116,124; 118,126; and 120,128. The locking pins 130substantially fix the reaction plate 66 and reaction cage 68 againstrelative fore and aft movement, along a line extending between left andright in FIG. 4.

As seen by reference additionally to FIGS. 9-12, the frame 64 andreaction cage 68 are releasably connectable in an operative statethrough a like cooperative arrangement of mounting tabs 132,134,136,138on the reaction cage 68 and 140,142,144,146 on the frame 64. Lockingpins 130 extend through the paired mounting tabs 132,140; 134,142;136,144; and 138,146 to substantially fix the frame 64 and reaction cage68 against relative fore and aft movement.

The reaction cage 68 has spaced walls 148,150, each generally in theshape of the letter “A”. The wall 148 carries the mounting tabs122,124,126,128, with the wall 150 carrying the mounting tabs132,134,136,138. Tubular reinforcing elements 152,154,156,158 connectbetween the walls 148,150 to unitize the reaction cage 68. Theconnection of each of the tubular reinforcing elements 152,154,156,158to its respective wall 148,150 is reinforced by gussets 160,162,164, asshown for the exemplary connection between the tubular reinforcingelement 156 and the wall 148. A reinforcing web 166 connects between thetubular reinforcing elements 152,154 and the walls 148,150.

Through this arrangement, the reaction force generated during operationof the cable pulling assembly 34 is transmitted from the frame 64 to thewall 150 and from there through the tubular elements 152,154,156,158 tothe wall 148 and to the reaction plate 66, which distributes the forceover the area to which the flat surface 84 on the reaction plate 66abuts.

The frame wall 96 has a flat surface 170, matched generally in shape tothe “A” shape of the wall 150 on the reaction cage 68, so as to transmitthe reaction force over the area of the flat surface 170 on the wall 168to an abutting flat surface 172 on the wall 150 over a substantial area.The wall 148 has a corresponding flat surface 174 which facially abutsto a flat surface 176 (FIGS. 4, 6) on the reaction plate 66, todistribute the reaction force over a substantial area of the reactionplate 66.

As seen in FIG. 4, the reaction cage 68 defines a working space at 178.Through the working space 178, the user/operator can manipulate thecable 22 and conduit 30 during setup and operation of the apparatus 12.

The frame 64 has a generally L-shaped construction defined by thevertically extending wall 96, and a horizontally extending wall 180.With the frame 64 and reaction 68 in assembled relationship, a tongue182 on the reaction cage 68 situates beneath a downwardly facing edge184 (FIG. 12) on the frame 64. The cooperation between the tongue 182and edge 184 facilitates alignment of the frame 64 and reaction cage 68.

The frame walls 96,180 are reinforced by a pair of spaced, L-shapedmounting braces 186,188 which define a mounting space 190 therebetweenfor the cable pulling assembly 34. Reinforcing gusseting 192, for theexemplary mounting brace 186, rigidifies the connection between themounting brace 186 and walls 96,180. The mounting brace 188 is similarlyreinforced through gusseting at 194.

The mounting braces 186,188 have the same construction. Exemplarymounting brace 186 has a horizontal leg 196 and a vertical leg 198 whichare configured to cooperatively, releasably support a traction supportassembly 200, which is shown in FIGS. 13-15, and which defines afoundation for the operating components of the cable pulling assembly34. The traction support assembly 200 consists of traction supportplates 202,204 that are joined, and maintained in spaced relationship,by a bottom pivot pin 206 and a separate bearing element/pin 208adjacent the top of the traction support assembly 200.

The traction support plates 202,204 are joined so as to cooperativelyproduce a combined width W (FIG. 14). The pivot pin 206 has a lengththat is greater than the width dimension W so that it defines stub shaftportions 210,212 projecting to beyond the walls 202,204, respectively.The bearing pin 208 has a similar length to define stub shaft portions214,216, respectively extending to beyond the traction support plates202,204. The width W is slightly less than the width W1 (FIG. 12) of themounting space 190 between the mounting braces 186,188 to allow aportion of the cable pulling assembly 34 to be directed therebetween, asexplained in detail below.

As seen additionally in FIG. 16, the mounting brace 186 has an upwardlyopening, U-shaped receptacle 218, with the mounting brace 188 having alike, upwardly opening receptacle 218′. With the bottom portion of thetraction support assembly 200 directed between the mounting braces186,188, the stub shafts 210,212 on the pivot pin 206 can be guided intothe receptacles 218,218′, respectively. The receptacles 218,218′ havecurved surfaces 220,220′ which cooperate with the stub shafts 210,212 toguide pivoting movement of the pivot pin 206 around a horizontal axis222 relative to the frame 64.

With the traction support assembly 200 initially separated from theframe 64, the traction support assembly 200 can be repositioned relativeto the frame 64 to direct the stub shafts 210,212 downwardly into thereceptacles 218,218′ so that a preassembly position, as shown in solidlines in FIG. 16, is realized. The traction support assembly 200 ischanged from the preassembly position into the operative position, shownin FIGS. 3-5 and in dotted lines in FIG. 16, by pivoting movement aroundthe axis 222 in the direction of the arrow 224 in FIG. 16. As thisoccurs, the stub shaft portions 214,216 on the bearing pin 208 move intoU-shaped receptacles 226,226′ in the mounting braces 186,188,respectively. The bases of the receptacles 226,226′ are defined bycurved surfaces 228,228′ which are complementary to the shape of thestub shaft portions 214, 216.

With the traction support assembly 200 in the operative position, areaction force generated by operation of the cable pulling assembly 34is caused to be simultaneously transmitted from the stub shafts 210,212to the curved surfaces 220,220′ bounding the receptacles 218, and fromthe stub shafts 214,216 on the bearing pin 208 to the surfaces 228,228′bounding the receptacles 226,226′. Through this arrangement, a reactionforce generated during operation of the cable pulling assembly 34 isdistributed to the frame wall 64, at vertically and horizontally spacedlocations, and from there to the wall 150 of the reaction cage 68.

The cable pulling assembly 34 can be conveniently assembled to andseparated from the frame 64 by practicing the steps described above.Accordingly, the cable pulling assembly 34 can be placed in itsoperative position, and maintained in the operative position, under itsown weight without the requirement of separate fasteners, by merelyrelatively repositioning the cable pulling assembly 34 and frame 64.Manipulation of the cable pulling assembly 34 is facilitated by theprovision of a U-shaped handle 230 at the top of the traction supportassembly 200. The handle 230 has a base 232 (FIGS. 3 and 5) and spacedlegs 234,236 extending from the base 232. The legs 234,236 areconnected, one each, to the stub shafts 214,216 on the bearing pin 208.

Details of the cable pulling assembly 34, consisting of the tractionsupport assembly 200, to which the operating components are mounted,will now be described with respect to FIGS. 17-30. An operatingcomponent package assembly, which is integrated into the tractionsupport assembly 200, is shown at 240. The operating component packageassembly 240 consists of the aforementioned drive/hydraulic motorassembly 104, a capstan assembly at 242, and a gear assembly at 244, fortransmitting a force from the drive/hydraulic motor assembly 104 to thepart 98 of the capstan assembly 242 to cause the part 98 of the capstanassembly 242 to be driven around the axis 102.

The capstan assembly part 98 has an annular shape with an outwardlyopening, U-shaped groove 246 formed continuously therearound. The groove246 is formed in a “wave” pattern fully around the axis 102. In thisembodiment, the wave pattern is regular throughout the circumferentialextent thereof. It is not required that the pattern be regular or thatthere be a specific amplitude or length for each wave, as explained ingreater detail below.

The theory of operation is as follows. In a conventional straight,non-wave groove, the cable 22, under tension, is squeezed radiallyinwardly into the groove and against a U-shaped surface bounding thesame. The traction force between the cable 22 and abutting groovesurface is substantially uniform along that portion of the groovesurface that is engaged by the cable 22. This force is generated througha wedging action as the cable 22 is drawn radially inwardly.

By using the wave pattern, the cable is caused to bend to nominallymatch the wave pattern. As the tension on the cable 22 increases, thecable 22 tends to straighten, which causes a localized pressure increasebetween the cable 22 and peaks 248 in the groove shape defined by thewave pattern, thereby enhancing the traction force on the cable 22. Theamplitude of each “wave” is thus selected to cause the generation oflocalized, increased pressure points, throughout the contact length,between the cable 22 and the capstan part 98 at the peaks 248.

The cable diameter and flexibility will determine the appropriateamplitude and frequency for each wave. At too great an amplitude and tooshort a wavelength, it may be difficult to conform the cable 22 to thegroove shape. A reduced wavelength and increased amplitude may alsoresult in the cable 22 not properly seating to the desired depth in thegroove 246 to benefit from the wedging action along the length. As shownin FIG. 28, this wedging action of the cable 22 in the groove 246 isprimarily responsible for the gripping between the cable 22 and capstanpart 98. If the wavelength becomes too long, and the amplitude toosmall, the operating characteristics approach that of a conventional,straight, non-wave groove.

The design also must take into account the fact that as the cable 22 isplaced under tension, its effective diameter reduces, as depicted inFIG. 29, whereby the tensioned cable 22 seats more deeply into thegroove 246. Thus, at the reduced diameter, it is desired that therestill be a relationship between the cable 22 and groove 246 that permitsthe requisite wedging action as the cable 22 is pulled in operation.

A typical cable diameter for this application is on the order of 0.75inch. However, this is a common diameter used in the industry and shouldnot in any way be viewed as limiting. If properly designed, as explainedin greater detail below, the wave groove may account for a substantialincrease in traction force over conventional grooves, potentiallyachieving traction forces similar to those resulting from multiple wrapsof the cable 22.

The capstan assembly 242 has a ring gear/annulus 250 with an annulararrangement of inner gear teeth 252 thereon. The annulus 250 isdrivingly engaged by the gear assembly 244, which in turn is driven bythe drive/hydraulic motor assembly 104. More specifically, the gearassembly 244 is a planetary gear assembly consisting of a sun gear 254and a plurality, and in this case five, planet gears 256. The number ofplanet gears 256 could be as few as two or greater than the five shown.The drive/hydraulic motor assembly 104 has an externally toothed output258 (FIG. 30) which is keyed within a socket 260 on the sun gear 254 sothat the sun gear 254 follows rotational movement of the output 258around the axis 102.

The sun gear 254 has two axially spaced, annular arrays of externalteeth at 262,262′, which are in mesh with corresponding annular arraysof external teeth 264,264′ on each planet gear 256. The teeth 264,264′are in turn in mesh with internal teeth 268,268′ on annular ground gears270,270′.

With the sun gear 254 driven in the direction of the arrow 272 in FIG.22 around the axis 102, the planet gears 256 are caused to be rotatedabout their respective axes 274 in the direction of the arrows 276. Asseen primarily in FIGS. 21 and 26, as the planet gears 256 move aroundtheir axes 274, an annular array of external teeth at 278 on each planetgear 256, between the teeth 264,264′, are in mesh with the teeth 252 onthe annulus 250, and drive the annulus 250 with the integralcable-engaging part 98 around the axis 102 in the direction of the arrow280.

The connection of the operating component package assembly 240 to thetraction support assembly 200 will now be described. A traction base 288is placed against an annular, axially facing surface 290 (FIG. 23) onthe capstan part 98. The traction base 288 has an annular rim 92 with anaxially facing, annular surface 294. The annular surface 294 defines aseat for a ball bearing assembly 296 with roller elements 298 that actbetween a radially inwardly facing surface 300 on the traction base 288,and a radially outwardly facing surface 302 on the capstan part 98.

A cover assembly 308 is then installed. The cover assembly 308 has afirst cover part 310 that is secured by fasteners 312 to the tractionbase 288. A second cover part 314 on the cover assembly 308 is in turnsecured to the first cover part 310 through fasteners 316. Appropriatesealing elements, such as those shown at 317 in FIG. 20, and well knownto those skilled in the art, can be interposed between the components.The detail of these sealing elements will not be described herein.

The traction base 288 has a peripheral edge 318 which is generally inthe shape of a triangle with three rounded apices 320. The tractionsupport plate 202 on the traction support assembly 200 has an opening322 formed therethrough that is nominally matched to the shape of theperipheral edge 318. The traction support plate 202 has formedreceptacles at 324, each designed to receive one of the apices 320 onthe traction base 288. Each receptacle 324 is bounded by a curvedsurface 326 which converges towards the center 328 of the opening 322.The traction base 288 is directed into the opening 322 in an axialdirection to bring the apices 320 into contact, one each, with thesurfaces 326 at each receptacle 324. By urging the surfaces 326 andtraction base 288 axially against each other, a centering/wedging actionis produced therebetween so that the traction base 288 and tractionsupport plate 202 become preliminarily held against relative pivotingaround the axis 102. A more positive keying against relative pivotingmovement is achieved by reason of the matching triangular shapes of thetraction base peripheral edge 318 and the opening 322 in the tractionsupport assembly 200. With the traction base 288 preassembled in thismanner, mounting clips 330 can be attached to the traction support plate202 to loosely, captively, maintain the traction base 288 in apreassembly position relative to the traction support assembly 200.

The traction support assembly 200 can then be reoriented with theloosely held traction base 288. The mounting clips 330 prevent thetraction base 288 from axially separating from the traction supportassembly 200 as this occurs. For convenience of assembly the tractionsupport assembly 200 can be oriented with the traction base 288 heldloosely thereto, so that the traction support plate 202 facesdownwardly.

The remaining components are assembled from the side of the tractionsupport plate 204 to captively embrace the traction support assembly200. More specifically, a corresponding traction base 288′, ball bearingassembly 296′, first cover part 310′, sealing element 317′, and secondcover part 314′ are sequentially installed, in the same manner as thecorresponding parts on the other side of the traction support assembly200, as previously described.

The traction support plate 204 has a construction corresponding to thetraction support plate 202, with receptacles 324′ around an opening 322′to receive apices 320′ on the traction base 288′. The receptacles 324′have surfaces 326′ corresponding in shape and function to the surfaces326.

With the operating component package assembly 240 fully assembled aroundthe traction support assembly 200, the surfaces 326, 326′ are captivebetween the traction bases 288, 288′. At the same time, the operatingcomponent package assembly 240 is confined against relative rotationaround the axis 102 by reason of the keyed connection between theperipheral edge 318 of the traction base 288 within the opening 322 anda like keying arrangement between a corresponding peripheral edge 318′on the traction base 288 and a corresponding opening 322′ on thetraction support plate 204.

Another aspect of the present invention is the provision of a cabletensioning assembly, as shown at 332 in FIGS. 9-12. The cable tensioningassembly 332 includes a cantilevered support 334 which carries, at itsfree end, a roller 336 for movement about a horizontally extending axis338. The roller 336 is aligned with the groove 246 in the capstan part98. As the cable pulling assembly 34 is pivoted from the preassemblyposition, shown in solid lines in FIG. 16, to the operative position,the roller 336 moves into the groove 246 at approximately the 8 o'clockposition in FIG. 4. During operation, the roller 336 acts against thecable 22 to locally urge the cable 22 radially inwardly into the groove246 to enhance the traction force production on the cable 22 by thecapstan part 98. As the cable tension is increased, the cable pullingassembly 34 is pressed with an increasing force towards the roller 336to increase the force produced by the roller 336 on the cable 22.

With the apparatus 12 set up, the cable 22, having the mole 26 attachedthereto, is directed through the reaction plate 66, the reaction cage68, and an opening 340 (FIG. 12) in the frame 64. The cable 22 iswrapped in the pattern shown in FIG. 4 around the capstan part 98beginning at the 12 o'clock position and extending through 270° toapproximately the 9 o'clock position, whereat the cable departs from thecapstan part 98 and projects vertically upwardly for appropriateaccumulation, at a location which is above ground in the FIG. 1arrangement. By manipulating the actuator 108 on the drive/hydraulicmotor assembly 104, valving on a valve block assembly 342 is placed in astate to cause driving of the output 258, which thereby actuates theplanetary gear assembly 244 to rotate the capstan part 98 around theaxis 102. The drive/hydraulic motor assembly 104 can be continuouslyoperated to produce a constant pulling force on the cable 22 to causethe mole 26 to move a substantial distance D1 through the composition14, and preferably the entire distance D between the first and secondlocations 16, 18. The switch assembly 110 will automatically cause abypass valve to divert flow of the hydraulic fluid at the valve block342 to interrupt the pulling force once the mole 26 has reached apredetermined position.

It should be understood that the above structure is exemplary in natureonly. The invention contemplates modifications to all different aspectsof the structure disclosed.

As just one example, the receptacles 218, 218′, shown on the frame 64,could be formed on the cable pulling assembly 34, to cooperate with anappropriate projection on the frame 64 to allow the requisite relativepivoting movement between the frame 64 and cable pulling assembly 34.

As shown in FIG. 31, and previously explained, the wave pattern for thegroove 246 on the cable-engaging capstan part 98, which is shown in anexaggerated form in FIG. 31, is regular and repeats throughout theentire circumferential extent of the groove 246. The wave pattern isshown with a wavelength (WL) and amplitude (A), with the amplitudemeasured from a reference plane P, axially bisecting the groove 246 andorthogonal to the axis 102, to the center line CL of the cable 22, whichis shown conformed to the contour of the groove 246 along thecircumferential extent thereof, depicted in FIG. 31.

The cable 22 is initially directed into the groove 246 and conformed tothe sinusoidal shape thereof. In operation, the cable 22, under tension,tends towards a straight length along a line orthogonal to the axis 102.This bears the cable 22 axially relative to the axis 102 against theaforementioned peaks at 248 whereby a circumferentially localized force,as indicated by the arrows F, is applied at each peak 248 to the cable22.

As seen in FIGS. 28 and 29, the groove 246 is defined by a U-shapedsurface 360 having axially spaced side portions 362, 364 which convergeto a radially opening bottom portion 366. The circumferentiallylocalized forces at the peaks 248 are applied to the cable 22 throughthe side portions 362, 364.

As previously noted, the wave pattern can be defined uniformly over theentire circumferential extent of the cable-engaging capstan part 98.However, myriad different groove configurations are contemplated. Theonly critical aspect of the groove configuration is that the tendency ofthe cable 22 to straighten, as it is placed under tension, will producea circumferentially localized pressure area or point on the cable 22that causes an enhanced traction force to be developed between thecapstan part 98 and cable 22. Generally, this will result with anygroove configuration in which the cable 22 is caused to change directionappreciably over a relatively limited circumferential length. As aresult, the centerline (CL) of the groove 246 has differentcircumferential locations that are spaced differently, in an axialdirection, along the capstan part 98, from the same reference plane P,as opposed to a conventional groove, wherein the center line residessubstantially in a single plane. At each such location, such as at thepeaks 248, the axial force component F is applied to the cable 22. If alocalized force is generated at more than one circumferential location,the effect on the traction force between the capstan part 98 and cable22 is cumulative.

In FIG. 32, a modified form of cable-engaging capstan part 98′ is shownwith a groove 246′ having a curved portion at 368. The curved portion368 may repeat around the circumference of the cable-engaging capstanportion 98′. Alternatively, only one such curved portion 368 may beprovided. As a further alternative, the curved portion 368 may beprovided in more than one location but not in a regular pattern aroundthe circumference of the cable-engaging capstan portion 98′. With thegroove construction shown, a peak 248′ is defined so that the sideportion 362′ of the groove surface 360′ produces a localized axial forceF on the cable 22 in the groove 246′.

In FIG. 33, a groove 246″ is shown having a curved portion at 368′,corresponding to the curved portion 368, but wherein the cable 22,operatively in the groove 246″, is required to change directions moreabruptly thereat. More specifically, the peak 248″ has a smaller radiuswhich produces more of a pinching action in an axial direction on thecable 22 through the force F. Additionally, whereas the groove 248′ iscontinuously curved over a substantial circumferential extent on thecable-engaging capstan part 98′, the curved portion 368′ on the capstanpart 98″ extends over a lesser circumferential length and is locatedbetween groove portions 370, 372 which are substantially straight andparallel to the travel direction, as indicated by the double-headedarrow 374. The travel direction is parallel to the reference plane P,corresponding to that in FIG. 31.

The groove 246′″ in FIG. 34 on the capstan part 98′″ correspondsgenerally to the configuration of the groove 246″ in FIG. 33 with theexception that the curved portion 368″ is approximated by an arc with alarger radius than that of the arc that approximates the curved portion368′. The force F produced on the cable 22 with the structure in FIG. 34may not be of the same magnitude as the force F generated in FIG. 33.

In FIG. 35, a groove 246″″ on a capstan part 98″″ has a meandering,curved configuration with peaks 248″″ defined at irregularcircumferential internals, and different axial positions on thecable-engaging capstan part 98″″. This results in the generation offorces F on the cable 22 at spaced circumferential locations withdifferent magnitudes.

In FIG. 36, a groove 246 ^(5x)′ on a capstan part 98 ^(5x)′ is shownwith a bent portion 378 defined by two generally straight portions at380, 382, angled with respect to the direction of travel, as indicatedby the double-headed arrow 384. The straight portions 380, 382 meet at acircumferential location at 386 at which the cable 22, operativelyengaged in the groove 246, must abruptly change directions. At thejuncture of the sections 380, 382, a sharpened peak 248″″ is defined atwhich an axial force F is applied to the cable 22.

The invention is not limited to a cable 22 that is wrapped less than360° around a cable-engaging capstan part. As shown in FIG. 37, acapstan 98 ^(6x)′ has a groove 246 ^(6x)′ extending in a spiral pathwith axially overlapping circumferential path portions 388, 390. One orboth of the circumferential portions 388, 390 has one or more curvedportions 368 ^(6x) to perform the function of the curved portions 368′,368″, previously described with respect to FIGS. 33 and 34,respectively.

The above groove configurations are intended only to be exemplary innature. Any structure that causes a circumferentially localized force tobe generated between a cable and cable-engaging capstan part iscontemplated by the invention.

While the construction of the planetary gear assembly 244 may bedesigned in many different ways by those skilled in this art, in oneform, the planetary gear assembly 244 is made as outlined in NASA TechBrief GSC-14207.

The foregoing disclosure of specific embodiments is intended to beillustrative of the broad concepts comprehended by the invention.

1. An apparatus for defining a passageway through a composition betweenfirst and second locations, the apparatus comprising: a cable pullingassembly; and a support for the cable pulling assembly, the cablepulling assembly comprising a capstan assembly, with a part of thecapstan assembly guided in movement around a first axis and engagablewith a cable connected to a mole so as to cause a cable engaged by thepart of the capstan assembly to be pulled as the part of the capstanassembly is driven around the first axis, the part of the capstanassembly comprising a circumferential groove, bounded by a surface andextending around the first axis, for reception of a cable to be pulled,the groove configured so that a circumferentially localized force isapplied by the groove surface to a cable operatively positioned in thegroove tending to avoid circumferential slippage between the part of thecapstan assembly and a cable operatively positioned in the groove. 2.The apparatus for defining a passageway through a composition betweenfirst and second locations according to claim 1 further in combinationwith a cable and a mole attached to the cable.
 3. The apparatus fordefining a passageway through a composition between first and secondlocations according to claim 1 wherein the groove extends continuouslyaround the first axis.
 4. The apparatus for defining a passagewaythrough a composition between first and second locations according toclaim 3 wherein the groove has an axial center and the axial center ofthe groove at a first circumferential location is spaced axially fromthe axial center of the groove at a second circumferential location. 5.The apparatus for defining a passageway through a composition betweenfirst and second locations according to claim 3 wherein the groove has acircumferential extent and the axial center of the groove has a curvedshape over at least a portion of the circumferential extent of thegroove.
 6. The apparatus for defining a passageway through a compositionbetween first and second locations according to claim 3 wherein theaxial center of the groove has a wave shape over at least a portion ofthe circumferential extent of the groove.
 7. The apparatus for defininga passageway through a composition between first and second locationsaccording to claim 1 wherein the surface defines an axial projectionwhich causes the circumferentially localized force to be applied to acable under tension within the groove.
 8. The apparatus for defining apassageway through a composition between first and second locationsaccording to claim 7 wherein the groove surface has axially spaced sideportions which converge to a radially opening bottom portion and theaxial projection is defined by one of the axially spaced side portions.9. The apparatus for defining a passageway through a composition betweenfirst and second locations according to claim 1 wherein the grooveextends in a spiral pattern around the first axis.
 10. The apparatus fordefining a passageway through a composition between first and secondlocations according to claim 1 wherein the cable pulling assemblycomprises a drive and a gear assembly operatively engaged between thedrive and the part of the capstan assembly to cause the part of thecapstan assembly to be driven around the first axis.
 11. The apparatusfor defining a passageway through a composition between first and secondlocations according to claim 10 wherein the gear assembly comprises aplanetary gear assembly.
 12. An apparatus for defining a passagewaythrough a composition between first and second locations, the apparatuscomprising: a cable pulling assembly; and a support for the cablepulling assembly, the cable pulling assembly comprising a capstanassembly, with a part of the capstan assembly guided in movement arounda first axis and engagable with a cable connected to a mole so as tocause a cable engaged by the part of the capstan assembly to be pulledas the part of the capstan assembly is driven around the first axis, thepart of the capstan assembly comprising a circumferential groove,bounded by a surface and extending around the first axis, for receptionof a cable to be pulled, the groove extending continuously around thefirst axis and having an axial center, the axial center of the groove ata first circumferential location spaced axially from the axial center ofthe groove at a second circumferential location.
 13. The apparatus fordefining a passageway through a composition between first and secondlocations according to claim 12 further in combination with a cable anda mole attached to the cable.
 14. The apparatus for defining apassageway through a composition between first and second locationsaccording to claim 12 wherein the groove has a circumferential extentand the axial center of the groove has a curved shape over at least aportion of the circumferential extent of the groove.
 15. The apparatusfor defining a passageway through a composition between first and secondlocations according to claim 12 wherein the axial center of the groovehas a wave shape over at least a portion of the circumferential extentof the groove.
 16. The apparatus for defining a passageway through acomposition between first and second locations according to claim 12wherein the surface defines an axial projection which causes acircumferentially localized force to be applied to a cable under tensionwithin the groove.
 17. The apparatus for defining a passageway through acomposition between first and second locations according to claim 16wherein the groove surface has axially spaced side portions whichconverge to a radially opening bottom portion and the axial projectionis defined by one of the axially spaced side portions.
 18. The apparatusfor defining a passageway through a composition between first and secondlocations according to claim 12 wherein the cable pulling assemblycomprises a drive and a gear assembly operatively engaged between thedrive and the part of the capstan assembly to cause the part of thecapstan assembly to be driven around the first axis.
 19. The apparatusfor defining a passageway through a composition between first and secondlocations according to claim 12 wherein the gear assembly comprises aplanetary gear assembly.
 20. A cable pulling assembly comprising: acapstan assembly having a part with a groove for receiving a cable to bepulled; and a drive through which the part of the capstan assembly isdriven around a first axis to cause a cable operatively positioned inthe groove to be pulled, the groove having a circumferential extentaround the first axis, the groove configured so that a circumferentiallylocalized force is applied by the groove surface to a cable operativelypositioned in the groove, tending to avoid circumferential slippagebetween the part of the capstan assembly and a cable operativelypositioned in the groove.
 21. The cable pulling assembly according toclaim 20 in combination with a cable and a mole that is connectable tothe cable to follow movement of the cable through a composition to forma passageway in the composition.
 22. The cable pulling assemblyaccording to claim 20 wherein the groove extends continuously around thefirst axis.
 23. The cable pulling assembly according to claim 22 whereinthe groove has an axial center and the axial center of the groove at afirst circumferential location is spaced axially from the axial centerof the groove at a second circumferential location.
 24. The cablepulling assembly according to claim 22 wherein the groove has acircumferential extent and the axial center of the groove has a curvedshape over at least a portion of the circumferential extent of thegroove.
 25. The cable pulling assembly according to claim 22 wherein theaxial location of the groove has a wave shape over at least a portion ofthe circumferential extent of the groove.
 26. The cable pulling assemblyaccording to claim 20 wherein the groove is bounded by a surface and thesurface defines an axial projection which causes the circumferentiallylocalized force to be applied to a cable under tension within thegroove.
 27. The cable pulling assembly according to claim 26 wherein thegroove surface has axially spaced side portions which converge to aradially opening bottom portion and the axial projection is defined byone of the axially spaced side portions.
 28. The cable pulling assemblyaccording to claim 20 wherein the cable pulling assembly comprises adrive and a gear assembly operatively engaged between the drive and thepart of the capstan assembly to cause the part of the capstan assemblyto be driven around the first axis.
 29. The cable pulling assemblyaccording to claim 28 the gear assembly comprises a planetary gearassembly.
 30. A cable pulling assembly comprising: a capstan assemblyhaving a part with a groove for receiving a cable to be pulled; and adrive through which the part of the capstan assembly is driven around afirst axis to cause a cable operatively positioned in the groove to bepulled, the groove having a circumferential extent around the firstaxis, the groove extending continuously around the first axis and havingan axial center; the axial center of the groove at a firstcircumferential location spaced axially from the axial center of thegroove at a second circumferential location.
 31. The cable pullingassembly according to claim 30 in combination with a cable and a molewhich is connectable to the cable to follow movement of the cablethrough a composition to form a passageway in the composition.
 32. Thecable pulling assembly according to claim 30 wherein the groove has acircumferential extent and the axial center of the groove has a curvedshape over at least a portion of the circumferential extent of thegroove.
 33. The cable pulling assembly according to claim 30 wherein theaxial location of the groove has a wave shape over at least a portion ofthe circumferential extent of the groove.
 34. The cable pulling assemblyaccording to claim 30 wherein the groove is bounded by a surface and thesurface defines an axial projection which causes a circumferentiallylocalized force to be applied to a cable under tension within thegroove.
 35. The cable pulling assembly according to claim 34 wherein thegroove surface has axially spaced side portions which converge to aradially opening bottom portion and the axial projection is defined byone of the axially spaced side portions.
 36. The cable pulling assemblyaccording to claim 30 wherein the cable pulling assembly comprises adrive and a gear assembly operatively engaged between the drive and thepart of the capstan assembly to cause the part of the capstan assemblyto be driven around the first axis.
 37. The cable pulling assemblyaccording to claim 36 the gear assembly comprises a planetary gearassembly.